September 23, 2013

Simulating three thousand years of history

There is a video in the press release for this paper showing how the simulation matches up with reality.

PNAS doi: 10.1073/pnas.1308825110

War, space, and the evolution of Old World complex societies

Peter Turchin et al.

How did human societies evolve from small groups, integrated by face-to-face cooperation, to huge anonymous societies of today, typically organized as states? Why is there so much variation in the ability of different human populations to construct viable states? Existing theories are usually formulated as verbal models and, as a result, do not yield sharply defined, quantitative predictions that could be unambiguously tested with data. Here we develop a cultural evolutionary model that predicts where and when the largest-scale complex societies arose in human history. The central premise of the model, which we test, is that costly institutions that enabled large human groups to function without splitting up evolved as a result of intense competition between societies—primarily warfare. Warfare intensity, in turn, depended on the spread of historically attested military technologies (e.g., chariots and cavalry) and on geographic factors (e.g., rugged landscape). The model was simulated within a realistic landscape of the Afroeurasian landmass and its predictions were tested against a large dataset documenting the spatiotemporal distribution of historical large-scale societies in Afroeurasia between 1,500 BCE and 1,500 CE. The model-predicted pattern of spread of large-scale societies was very similar to the observed one. Overall, the model explained 65% of variance in the data. An alternative model, omitting the effect of diffusing military technologies, explained only 16% of variance. Our results support theories that emphasize the role of institutions in state-building and suggest a possible explanation why a long history of statehood is positively correlated with political stability, institutional quality, and income per capita.

9 comments:

The abstract suggests circularity here (the full article may deal with this, perhaps) in that "the central premise...is...warfare", and unsurprisingly military technology then explained most of the variance.

"The central premise of the model, which we test, is that costly institutions that enabled large human groups to function without splitting up evolved as a result of intense competition between societies—primarily warfare. "

Too bad for this thesis that the first unitary states coalesced around irrigation.

Tribal warfare is eons older than organized states, but the rise of state level societies was obviously not a random occurrence. I am of the mind that population growth within a restricted region, and the resulting inter-group competition for increasingly limited resources, was instrumental. Thus, no states were viable, and no states were built, before the massive population expansions of the Neolithic period.

That state formation is driven by inter-group competition is validated by the domino effect of state genesis: when one state level society rises in a region, other state level societies are quick to follow. But before population density reached a decisive stage in communities, states did not form because, first of all, there wasn't enough people within a specific distance to coalesce, and second, there was no incentive because tribes were capable of surviving without stepping on one another's toes.

Of course, that didn't prevent tribal warfare from breaking out over petty differences. But such conflicts stayed limited in scope - ie within the face-to-face networks of early tribes - and did not lead to the creation of large polities.

You can see that for a while, fragmented regions can be viable if they are held together by a common language. On the flip side, fragmentation certainly means a disadvantage in both local and international trade, and for better or worse, those areas missed out on the colonization boon.

The hallmark of state formation is monumental architecture. Sites like Göbekli Tepe, Caral and Sechín Bajo prove that it was religion what triggered state formation. Early states were theocracies. People have looked for archaeological signs of war at early states and found no evidence. They should abandon the war hypothesis already.

1Marcelo,"Sites like Göbekli Tepe, Caral, Sechín Bajo, etc. indicate that it was religion what triggered state formation."

This begs the question. It assumes a form of religion that requires these edifices. But what drives that particualr form of religion? Navajo religion is complex and intense and yet it requires, allows for, no temples at all. What drove these societies to develop this particualr form of religion you refer to?

Lathdrinor,

"I am of the mind that population growth within a restricted region, and the resulting inter-group competition for increasingly limited resources, was instrumental. Thus, no states were viable, and no states were built, before the massive population expansions of the Neolithic period."

The key is population density and competition for resources, not agriculture, since you can have that density and that comeptition in forager societies if the environment is rich enough - the Pacific Northwest, for instance. Who knows how long their salmon-based economy was going?

This paper probably does its relational asumptions on an overated subject: war. Richness of production and trade lead to war or the arts. Or both. And historians love both. War is always overated whereas other factors, say trade (my favorites)is underated by historians. War makes a great history subject. We know that from Homer, Thucides et all... Trade (and by chance I was looking at medieval trade books this morning say Lopez and Spuford) is a low class people subject. Who writes about the Phoenicians? they were not warriors but mostly traders, quite autonomous with no central power but a net of cities. And then there is Hamilcar and Hannibal, but many centuries later.

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